Modulating system



Dec. 9, 1930. J NUMANS 1,784,610

' MODULATING SYSTEM Filed May 21, 1927 INVENTOR JDHANNES JkEQUES NUMANS AT RNEY forms part of the grid leak cf; the firstorder to be. able at any instant to verify the value of the grid currents of the oscillator O.

Patented Dec. 9, 1930 oF-FicE JOHANNES JAccnEsNUMAivs, or nnvnnovnn, NETHERLANDS, Assreivon ro BADIQ CORPORATION or A ERIC A CORPORATION OF DELAWARE MODULATING- sYs'rE Application filed May 21, 1927, Serial No; 193,201, and in the Netherlands May 22, 1926.1

The invention relates to a circuitarrange ment for modulating the oscillations generated or amplified by a thermionic device, for example, for periodically interrupting or altering these oscillations by means of a 51g. nal-key or for acoustically modulating these oscillations with the aid of a microphone or similar device.

. The invention has for its object a circuit arrangement. which permits low tensions to be applied continuously to the modulating member so that under all circumstances there is no danger in touching it even with transmitters of large outputs which are operated with high tensions and comparatively heavy currents because of their large outputs. The

invention has also for its object to prevent the production of strong sparks so that signals can be transmitted with great rapidity.

According to the invention, this. purpose is attained by-so arranging thecircuit that the modulating member acts upon the internal resistance of a first auxiliary triode conne'cted in series with an ohmic resistance which forms part of the. grid'circuit of a second auxiliary triode which in ,.its turn mentioned thermionic device. 7

Further features of the invention will appear from what follows and the invention Willbe explained in detail with reference to I the accompanying drawings in which;

Figs, land 2 show'enibodiinents of the modulating, system. In the figures which only represent two embodiments of the principle of theinvention, O is a triode which serves togenerate the desired oscillations or to amplify the oscillations generated by a preceding tr1ode, and which is connected 1n denser C is shown. I

The grid leak consists of a self induction coil L connected in series With an ohmic resistance W the Whole of it being connected in serles witha triode T H. 'Moreover, an ammeter A is joined to the arrangement 1n I The grid circuit of the auxiliary triode T V H comprises a grid biasing battery B" and an adjustable'ohmic resistance R, the dimensions being so chosen that under the influence of the negative potentialof the grid of the triode T H owing to the tension of the battery, V B the internal resistanceof the said triode is :just, sufficient to cause grid currents of the desired value to flow in the oscillator O. WVhen the negative potential of thegrid of the triode THiincreases with respect to the filament, the internal resistance of this triode increases and thegrid currents vin O decreases. This increase of the negative potentialof the grid of the triode T H of potential S is a s'ource'of direct current keeping in mind the rectifying properties of the triodes E H and T H, this source S may be replaced by an alternating current source, for example, by a transformer as illustrated in Fig. In that case, the frequencyof this alternatingcurrent source should preferably be chosen so as to lie in the ultra-audible region. In the grid circuit of the triode E H is included a battery B which has-its negative =pole connected to the grid and its positive pole to a modulator M which, in the example illustrated, is a signal key but it maybe any form of modulator.

, Furthermore the grid connected by a leakage resistance L W.

The operation of the invention is as follows When the key ispressed down, the grid of the triode EH has a negative potential equal to the potential of the battery B. This potential is chosen so that the internal resistance of the triode E H practically becomes in-- finitely great, and thereforetlie source of current S cannot supply current. 7

When the key is released, the charge on the grid of the triode E H leaks away along the leakage resistance L W and. the currentof the, battery S is allowed to pass. This curp p I andkthecathode of. the first auxiliary triode E H are mutually source of current S stops flowing so that the potential of the grid of the triode T H is also restored again to its normal value.

t will beevideiit that the circuit-arrange ment can also be used for telephony purposes, in whichcase the key M need onlybe replaced by a microphone olisuitable size.

The circuitarrangement affords the advantage'that at the modulator M only very slight potentials and break-induced currents are concerned. The working contact-of the key can even beearthed without any disadvantage. The closing and the interruption of the current are'efiected without any appreciable inertia so that even in that respect the arrangement, has advantages over the known interruption relays which, because of their high tensions, have their contacts so Widely spaced apart that the transmission of signals can only take place slowly. I

The E. M. F. of the source of potential S should be rather high (for example, of the order offmagnitude of some thousands of volts) as during the time intervals between the sigi'iallingperiods, the average grid potential of the triode O is determined thereby and it is desirable to keep this potential strongly negative.

What I claim is: v

1; A circuit arrangement for, modulating oscillations, comprising an oscillating tube, a grid leak for said tube, a modulating member, an auxiliary triode, a. second auxiliary triode having its filament conductively connected to the grid of said oscillating tube, and an ohmic resistance which forms part of the grid circuit of the second auxiliary triode, the modulating member acting upon the internal resistance of the first auxiliary triode, the' first auxiliary tr ode, the ohmic resistancewhich forms part of the grid circuit 1;

of the second auxiliary triode, and thesecond auxiliary tube being connected 111 series, the

second auxiliary triode forming part of the grid leak of the oscillating member.

2A circuit arrangement for modulating oscillations, comprising an oscillating tube, a grid leak for said tube, a modulatingmemher, an auxiliary triode, a second auxiliary triode, an ohmic resistance which forms part of the grid circuit of the second auxiliary triode, the modulating member acting upon the internal resistance of the first auxiliary triode, the first auxiliary triode being connected in series with the ohmic resistance which forms part of the grid circuit of the second auxiliary triode, the second auxiliary triode forming part of the grid leak of the oscillating member, and a source of potential conductively connected between the grid and the cathode of the first auxiliary triode so as to be in series with the modulating member.

3. A circuit arrangement for modulating oscillations, comprising an oscillating tube, a grid leak for said tube, a modulating member, an auxiliary triode, a' second auxiliary triode, an ohmic resistance which forms part of the grid circuit of the second auxiliary triode, the modulating member acting upon the internal resistance of the first auxiliary triode, the first auxiliary triode being connected in series with the ohmic resistance which forms part of the, grid circuit of the second auxiliary triode, the second auxiliary triode forming part of the grid leak of the oscillating member, a source of otential connected between the grid andt e cathode of the first auxiliary triode so as to be in series with the modulating member, and a leakage resistance arranged between the grid and the cathode of the first auxiliary triode.

' 4. A circuit arrangement for modulating oscillations, comprising an oscillating tube, a grid leak for said tube, a modulating member, an auxiliary triode, asecond auxiliary triode, an ohmic resistance which forms part of the grid circuit of the second auxiliary triode, the modulating member acting upon the internal resistance of the first auxiliary triode, the first auxiliary triode being connected in serieswith the ohmic resistance which forms part of the gridcircuit of the second auxiliary triode, the second auxiliary triode forming part of the grid leak of the oscillating member, the ohmic resistance which forms part of the grid circuit of the sec-0nd auxiliary triode also forming part of the discharge cathode anode path of the first auxiliary triode,,and a source of direct'current potential, the plate circuit of the first auxiliary triode being connected in series with the source of direct current potential;

5. A circuit arrangement for modulating "oscillations, comprising an oscillating tube,

a grid leak for said tube, a modulating meme'r, an auxiliary triode, a second auxiliary triode, an ohmic resistance which forms part of the grid circuit of the second auxiliary triode, the modulating member acting upon the internal resistance of the first auxiliary triode, the first auxiliary triode being connected in series with the ohmic resistance which forms part of the grid circuit of the second auxiliary triode,the second auxiliary triode forming part of the grid leak of the oscillating member, the ohmic resistance which forms part of the grid circuit of the second auxiliary triode also forming part of the discharge cathode anode path of the first auxiliary triode, and a source of direct current potential, the plate circuit of the first auxiliary triode being connected in series With the source of direct current potential, the grid of the second auxiliary triode being biased.

6. In a circuit arrangement for modulating oscillations an oscillation tube, a grid leak for said tube comprising an inductance a fixed resistance and a variable resistance all connected electrically in series, an auxiliary tri0cle,'a source of potential connected between the grid and the cathode of said auxlliary triode, a modulating means adapted to vary the internal resistance of said auxiliary triode and means controlled thereby for varying the value of said variable resistance in accordance therewith.

J OHANNES JACQUES NUMANS. 

